1. Field of the Invention
The present invention relates to an ophthalmic apparatus capable of aligning an optometric unit with an eye to be examined by manipulating an operation member to examine, observe, and capture the eye to be examined, a method of controlling the ophthalmic apparatus, and a storage medium.
2. Description of the Related Art
In an ophthalmic apparatus such as a noncontact tonometer, it is necessary to align an optometric unit with an eye to be examined so as to attain a predetermined positional relationship. There are known many products that adopt a joystick as an operation member for moving the optometric unit in the upward/downward, forward/backward, and leftward/rightward directions for this alignment adjustment. In general, the joystick of the ophthalmic apparatus can perform a “fine motion” operation of finely moving the optometric unit for fine alignment with the eye to be examined and a “coarse motion” operation of coarsely moving the optometric unit for coarse alignment.
An electric joystick has recently been developed, which implements the fine motion operation and the coarse motion operation by using electric driving and control methods (Japanese Patent Laid-Open No. 2002-369799, to be referred to as “patent literature 1” hereinafter). The joystick of patent literature 1 is mechanically configured to make the optometric unit perform “fine motion” when being manipulated in a predetermined skew angle range (for example, from −20° to +20°) and to make the optometric unit perform “coarse motion” when being manipulated beyond the predetermined skew angle range.
When aligning the optometric unit with an eye to be examined, an examiner who is inexperienced in the operation may largely move the optometric unit by erroneously manipulating the joystick into the coarse motion range against his/her intention. This not only prolongs the time up to completion of alignment but also may bring the optometric unit into contact with the eye to be examined, raising fears of the object. To solve the above-described problem, for example, Japanese Patent No. 03672447 (to be referred to as “patent literature 2” hereinafter) proposes a control method of stopping Z (forward/backward direction) direction movement until alignment in the X and Y (leftward/rightward and upward/downward) directions is completed. Japanese Patent Laid-Open No. 2004-275504 (to be referred to as “patent literature 3” hereinafter) proposes a control method of reducing the speed of alignment in the X and Y directions near the eye to be examined in accordance with a predetermined weight. Japanese Patent No. 04265842 (to be referred to as “patent literature 4” hereinafter) solves the problem by changing the moving speed up to completion of alignment in accordance with the misalignment amount between the eye to be examined and the optometric unit.
However, the arrangements of patent literatures 2 and 3 are specialized in contriving alignment in the X and Y directions. Hence, at the time of alignment in the Z direction after alignment in the X and Y directions, the optometric unit may be moved toward the eye to be examined at a high speed. Patent literature 4 includes no detailed description about misalignment detection in the Z direction, and it is therefore difficult to control the speed in the Z direction based on the misalignment amount in the Z direction. In addition, all patent literatures 2, 3, and 4 solve the problem by compromising the original operability ensured by combining fine motion and coarse motion of the joystick.